WASHINGTON: The Obama administration said Thursday it would support tougher economic pressure on Iran if the Islamic Republic doesn’t begin slowing the pace of its uranium enrichment activity and opening its stockpiles of nuclear material to greater inspection, and reassured its critics that the United States would not be played for fools by the moderate tone of Iran’s new leader.

The chief U.S. nuclear negotiator told the Senate Foreign Relations Committee that the administration could offer the Iranians some sanctions relief as “confidence-building” measures but that it would support new and tougher trade restrictions from Congress if diplomacy ultimately fails to ease concerns that Iran might be trying to develop nuclear weapons.

“I’m saying this” to Iran, said negotiator Wendy Sherman, who will meet with other world powers and Iran in Geneva in two weeks. “Come on the 15th of October with concrete, substantive actions that you will take, commitments you will make in a verifiable way, monitoring and verification that you will sign up to, to create some faith that there is reality to this, and our Congress will listen.

Speaking in Tokyo, Secretary of State John Kerry said the United States would not be played for “suckers” by Iranian President Hassan Rouhani. Still, Kerry defended President Barack Obama’s recent engagement effort.

The Senate Banking Committee is expected to draft a new sanctions package later this month, mirroring legislation passed by the House in July that blacklists Iran’s mining and construction sectors and commits the United States to the goal of eliminating all Iranian petroleum sales worldwide by 2015. The administration had expressed concern about the sanctions undercutting Rouhani with hardliners in his own country or weakening the international consensus on Iran.

Sherman asked senators, however, to wait until after the Geneva talks before moving forward.

Kerry, responding to Israeli Prime Minister Benjamin Netanyahu’s urging not to trust Iran, defended the engagement effort. Kerry met last week at the United Nations with Iranian Foreign Minister Mohammad Javad Zarif, and then Obama placed a historic phone call to Rouhani — the first between U.S. and Iranian leaders in more than three decades.

He said it would be “diplomatic malpractice of the worst order” not to test at least Iran’s rhetorical promises that it is prepared to negotiate.

However, he added, “there is nothing here that is going to be taken at face value, and we have made that clear.”